The blood group antigen binding activity of the Helicobacter pylori baba adhesin is regulated by local ph and redox potential

The surface appendages of bacteria determine the initial contact with host cells. Characterisation of functional organisation and spatial distribution of adhesive traits of outer membrane components of Gram-negative bacteria is a key issue in studies of the parasite-host cell interaction.With focus on the enteropathogenic Helicobacter pylori, evidenced to cause chronic gastric infections in humans, detergent-digested freeze fracture replica labelling was applied for ultrastructural analyses of envelope distribution of the virulence factors blood group antigen binding adhesin (BabA), and the carbonic anhydrases (α-CA, s-CA). In a preliminary study the methodology was also used to study the bacteria-host contact between phagocytosing human neutrophils and wild-type H. pylori.In parallel, bacterial traits were analysed from a molecular and biochemical perspective. This included the specific roles of the BabA and the sialic acid-binding adhesin (SabA), and the neutrophil activating protein (HP-NAP) in neutrophilic stimulation and subsequent inflammatory process. It was concluded that SabA is crucial in the initiation of a neutrophilic response in the mediated inflammation.This thesis has demonstrated the synergistic application of ultrastructural, molecular and cellular microbiology tools for delineating complex patterns in bacteria-host interactions, thus utilising the well-characterised and clinically important human pathogen H. pylori. This approach could be applicable to other Gram-negative species to clarify known and discern new virulence mechanisms in the multifaceted field of bacterial pathogenesis and bacterial interactions with human host cells.